JPS6046621B2 - Electric field mitigation device for insulation coated terminal of conductor with back electrode configuration - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric field relaxation device for preventing partial discharge or smooth surface discharge at a stator coil end in a rotating electric machine.

In particular, the present invention relates to a device for preventing smooth surface discharge at the end of a stator coil or the end of a cable, which constitutes a back electrode structure.

Recently, due to the development and practical application of high-performance organic or inorganic insulating materials, the rated voltage of stator coils has increased due to the increase in voltage and single capacity of rotating electric machines. Electric field relaxation has become an important issue.

The above-mentioned problem is an important problem not only during daily operation of a rotating electric machine but also during a dielectric strength test conducted in accordance with the Electrical Standards Committee standard JEC-114 (1964).

As shown in FIG. 1, the electric field relaxation device at the stator coil end includes a low-resistance corona shield layer 6 on the surface of the main insulating layer 5 extending from the slot 2 of the stator core 1 to the involute portion of the stator coil 3. Generally, an electric field relaxation layer 7 is provided on the surface of the main insulating layer 5 on the coil end side of the low-resistance corona shield layer 6 at a portion where the smooth surface potential gradient becomes large.

When a voltage is applied to the conductor 4 of the stator coil 3 having such a structure, the coil end portion has a back electrode configuration in which the conductor 4 and the ground electrode formed by the low resistance corona shield layer 6 are respectively electrodes. , the lines of electric force between the electrodes cross the surface of the main insulating layer 5, and the capacitance between the opposing electrodes is large, so the potential gradient in the direction of the smooth surface of the coil on the surface of the main insulating layer 5 becomes large. .

In particular, the potential gradient becomes extremely large at the end portion of the low-resistance corona shield layer 6, which serves as the ground electrode, and partial discharge or smooth surface discharge is likely to occur in the portion where the potential gradient is large. The electric field relaxation layer 7 is provided in a portion where the potential gradient becomes large. The electric field relaxation layer 7 is formed by coating a high resistance paint with linear resistance characteristics or an electric field relaxation paint with voltage non-linear resistance characteristics, but in general, the latter material is used to reduce the electric field due to characteristics and workability. A relaxation layer 7 is applied.

In addition, electric field relaxation paints with voltage non-linear resistance characteristics have a property that the resistance changes non-linearly with respect to the electric field, and in low electric fields, they exhibit a resistance value comparable to that of an insulator.
It is made of a material that exhibits a resistance value comparable to that of a semiconductor in a high electric field.

The electric field relaxation behavior of the conventional example of the electric field relaxation layer 7 using the electric field relaxation paint as described above is as shown in FIG.
The equivalent circuit at the coil end of Yang Kai's stator coil 3 where an alternating current voltage is applied to the conductor 4 of the stator coil 3 is as shown in Figure b, where X is the coordinate in the coil creeping direction. Resistance R of layer 7 and capacitance C of main insulating layer 5
It will be displayed as In this case, the distribution of the surface potential (2) of the electric field relaxation layer 7 becomes a curve 10 shown in FIG. A charging current is generated in the main insulating layer 5 based on the potential difference between the electric field relaxation layer 7 and the conductor 4. This charging current is integrated in the electric field relaxation layer 7 and flows into the low resistance corona shield layer 6. Therefore, the distribution of the current J flowing through the electric field relaxation layer 7 in the axial direction of the stator coil 3 becomes maximum at X=0. Control electric field Em in this electric field relaxation layer 7
The multiplicative product of the current J and the current J can be expressed as the power consumption EmJ in the electric field relaxation layer 7. The distribution becomes like the curve 11 shown in d of the same figure. In this case, the Joule heat generation amount based on the power consumption EmJ of the electric field relaxation layer 7 is approximately EmJ
The temperature of the electric field relaxation layer 7 near X=0 is extremely high! It becomes.

In general, electric field relaxation paints undergo thermal breakdown when the temperature rises and lose their ability to relax electric fields, which is the original function of electric field relaxation paints, causing creeping discharge or partial discharge on the surface of the electric field relaxation layer 7 of the stator coil 3. ·vinegar.

As a result, in the main insulating layer 5, thermal deterioration occurs in the vicinity of the electric field relaxation layer 7 where the temperature has significantly increased, and discharge deterioration due to creeping discharge and partial discharge occurs, and the progress of this deterioration causes a short circuit accident. . Furthermore, during a dielectric strength test, if the above-mentioned thermal breakdown or discharge occurs at a voltage below a predetermined applied voltage, the dielectric strength test cannot be performed, so there is a limit to the applied voltage to which the electric field mitigation paint can be applied.

Therefore, in order to prevent the above-mentioned accidents and to increase the applied voltage to which the electric field relaxation paint can be applied, it is necessary to prevent thermal destruction of the electric field relaxation layer 7 due to Joule heat generation of the electric field relaxation paint. This invention has been made in view of the above points, and includes providing a voltage dividing electrode via a dielectric on the outer periphery of the electric field relaxing layer 7, and electrically connecting one end of the voltage dividing electrode to the middle of the electric field relaxing layer 7. This connection is intended to reduce the current J flowing through the electric field relaxation layer 7, thereby eliminating the drawbacks of the above-mentioned conventional devices.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 3a is a partial sectional view showing a basic embodiment of the present invention, in which a dielectric 9 made of a border such as mica tape is applied around the outer periphery of the electric field relaxation layer 7, and a dielectric material 9 made of a conductive foil is further applied. The piezoelectric electrodes 8 are sequentially provided, and the partial pressure electrodes 8a, 8b and 8
One end of c is electrically connected to the electric field relaxation layer 7 at distances Ll, l-2, and L from X=0, respectively.

The material, shape, and size of the dielectric 9 and the partial voltage electrode 8 are not particularly limited, and the dielectric 9 may be made by winding conventionally used mica tape, or by winding conductive metal foil. It may be formed as the voltage dividing electrode 8.

Note that it is effective if the dielectric body 9 is formed of a material having a large dielectric constant and a high breakdown voltage characteristic.

Furthermore, when using mica tape, the effect is the same even if it is impregnated with an impregnating resin and hardened. The equivalent circuit at the coil end of the stator coil 3 with AC voltage applied to the conductor 4 of the stator coil 3 configured as described above is as shown in FIG. Partial voltage electrode 8a
, the dielectric 9 portions inserted between the voltage dividing electrodes 8a and 8b1, the voltage dividing electrodes 8b and 8C1, and the voltage dividing electrode 8c and the conductor 4 have capacitances Cl, C2, C3 and C4, respectively.
are connected in series, and the Cl, C2, C3
It can be displayed that one end of each of C4 and C4 is connected to one end of the resistor representing the electric field relaxation layer 7, X=0, at a distance of Ll, Ll+L2, L1+L2+L3 from X=O. Further, since the other end of C4 has the same potential applied to the conductor 4, it can be shown by a circuit electrically connected to the non-grounded side of the AC power supply representing the conductor 4.
In this case, compared to the resistances of Ll, L, L3 and the remaining end of the electric field relaxation layer 7, Cl, C2
, C3 and C4 are sufficiently small.
The potentials of the partial voltage electrodes 8a, 8b and 8c are Cl, C2,
It is forcibly controlled by the capacitance-divided potential of C3 and C4.

Therefore, the distribution of the surface potential (2) in the electric field relaxation layer 7 becomes as shown by a curve 12 shown in FIG. That is, since the electric field relaxation layer 7 potential (2) is forcibly controlled by the potentials of the partial voltage electrodes 8a, 8b, and 8c, the curve 10 in the conventional embodiment
A curve 12 is obtained in which the potential increases with a gentler slope than the slope of . Further, the distribution of power consumption EmJ in the electric field relaxation layer 7 is as shown by a curve 13 shown in d of the figure.

That is, as shown in the distribution of the potential (2) above, the gradient thereof is given as the control electric field Em of the electric field relaxation layer 7, and the Em of the curve 12 is smaller than the Em of the curve 10. Furthermore, the current flowing through the electric field relaxation layer 7 based on the charging current generated in the main insulating layer 5 is considerably shunted to Cl, C2, and C3 having low impedance through the voltage dividing electrodes 8a, 8b, and 8c. The current J flowing into the low-resistance shield layer 6 decreases. That is, the power consumption EmJ in the electric field relaxation layer 7, which is given by the multiplicative product of the control electric field Em and the current J, is much smaller than the curve 11 and has a substantially uniform distribution as shown in the curve 13.
Therefore, the distribution of Joule heat generation in the electric field relaxation layer 7 based on the power consumption of the curve 13 becomes almost uniform, and the temperature rise thereof is much lower than in the conventional embodiment.

However, since the temperature at which the electric field relaxation paint thermally breaks down is approximately constant, the applied voltage that caused the electric field relaxation layer 7 to break down in the conventional example does not break it in the embodiment of the present invention.

That is, it will be easily understood that the applied voltage that destroys the electric field relaxation layer 7 increases. In addition, in this invention, the dielectric material 9 and the voltage dividing electrode 8 are smaller than the resistance R of the electric field relaxation layer 7.
The capacitance Ql, C2, C3 and C
The effect of the present invention is remarkable when the impedance of resistor 4 is sufficiently small, but the ratio of the resistor R<5 to the impedance of C1, C2, C3 and C4 is not particularly limited.

In the embodiment described above, the number of voltage dividing electrodes 8 is three, but the larger the number of voltage dividing electrodes 8, the better, and the number is not particularly limited.

That is, it can be set as appropriate depending on the number of voltage dividing electrodes 8, the distance between the electrodes, the sizes of the capacitances Cl, C2, C3, and C4, or the magnitude of the applied voltage. Also,
The effect becomes particularly remarkable when an electric field relaxation paint with voltage non-linear resistance is applied to the electric field relaxation layer 7, and it can also be applied when the electric field relaxation layer 7 has linear resistance characteristics. Effects can be obtained. The equivalent circuit at the coil end of the stator coil 3 can be expressed as an RC equivalent circuit of the resistance R of the electric field relaxation layer 7 and the capacitance C of the main insulating layer 5, as shown in FIG. 2b.

When the electric field relaxation layer 7 is not provided, it can be represented by an equivalent circuit of the surface resistance R of the main insulating layer 5 and the capacitance C of the main insulating layer 5.

That is, taking FIG. 3 of the present invention as an example, the surface resistance R of the main insulating layer 5 can be expressed by the interfacial resistance between the main insulating layer 5 and the dielectric 10. However, since the magnitude of the resistance R is different between the case where the electric field relaxation layer 7 is provided and the case where it is not provided, the distribution curve 12 of the potential V and the distribution curve 13 of the power consumption EmJ shown in FIGS. 3c and d are different. The distribution state is different. Since the present invention can be applied to anything that can be expressed as an RC equivalent circuit, the same effect can be achieved even when the electric field relaxation layer 7 is not provided.

Note that the method of the present invention applies to the main insulating layer 5 of the stator coil 3.
It is easy to understand that this has no effect on the

The above explanation is about the stator coil of a rotating electric machine, but the same effect can be obtained by applying it to the end of the cable, where the cable conductor and the outer ground sheath each serve as electrodes to form a back electrode structure. It is something that can be played.

As described in detail above, in the electric field relaxation device for the insulation coated terminal of a conductor having a back electrode configuration according to the present invention, the low resistance corona shield layer and the main insulation layer surface or electric field relaxation layer connected thereto are surrounded through a dielectric. A partial voltage electrode is provided, and one end of the voltage dividing electrode is electrically connected to the surface of the main insulating layer or the middle of the electric field relaxation layer, and the surface of the main insulation layer 5 continuous to the corona shield layer or the electric field relaxation layer. This can significantly reduce the power consumption of the main insulating layer surface or electric field relaxation layer, thereby preventing a significant increase in applied voltage or short-circuit accidents that could lead to breakdown of the main insulating layer surface or electric field relaxation layer. It can have great practical effects, such as being able to prevent.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the structure of a part of the stator coil of a rotating electric machine, Fig. 2 a-d is a partial cross-sectional view showing the structure of a conventional electric field relaxation layer and its explanatory diagram, and Figs. 3 a-d 1 is a partial sectional view and an explanatory view of an embodiment of the present invention. In the figure, 1 is a stator core, 2 is a slot, 3 is a stator coil, 4 is a conductor, 5 is a main insulating layer, 6 is a low-resistance corona shield layer, 7 is an electric field relaxation layer, 8a, 8b and 8c are separated. A piezo electrode, 9 is a dielectric, 10 and 12 are curves showing the distribution of electric potential (2), and 11 and 13 are curves showing the distribution of power consumption EmJ.

Claims (1)

[Claims] 1. A low-resistance corona shield layer that covers the insulation coating of a conductor having a back electrode configuration, leaving only the terminal portion, and an electric field relaxation layer having linear or nonlinear voltage characteristics that covers the insulation coating terminal portion following the low-resistance corona shield layer. The electric field relaxation layer and the low-resistance corona shield layer are surrounded by a dielectric layer, and one end of each is in contact with the surface of the electric field relaxation layer, and each contact side end is connected to the adjacent next layer. An electric field relaxation device for an insulating coating terminal of a conductor having a back electrode configuration including a plurality of partial voltage electrodes surrounded by the dielectric layer and configured in a laminated manner at the non-contact side end of the stage.